Process and apparatus for measuring spectral response of solar cell, and process for compensating decay of light source

Abstract

The invention employs a group of LED devices as a light source for emitting light with different wavelengths towards the solar cell under test. A set of test signal data composed of mutually orthogonal test signals are used to power the LED devices to emit light. The solar cell, upon receiving light from the LED devices powered by the test signal data, generates detected values which are in turn converted into electric signals. A processor device is then used to separate component signals contributed by the respective LED devices from the signals and compare the component signals to the output power level corresponding to the test signal data and/or to the optical energy levels radiated from the respective LED devices, thereby obtaining the spectral response of the solar cell to the different wavelengths of light.

1 . A process for measuring a spectral response of a solar cell by using a light-emitting diode (LED) array as a light source for emitting light towards the solar cell, the LED array comprising at least one group of LED devices with each group having a plurality of LED devices, wherein the LED devices are capable of emitting multiple types of light having different central wavelengths from one another and the different types of light have a total number equal to or less than the total number of the LED devices, the process comprising the steps of:
 a) powering the at least one group of LED devices to emit light in a synchronized manner by providing a set of test signal data composed of multiple test signals, wherein the test signals are mutually orthogonal to one another and have an output power level corresponding to at least one known power level;   b) converting detected values generated by the solar cell upon detecting light from the group of LED devices powered by the set of test signal data into detected electric signals; and   c) using a processor device to separate component signals contributed by the respective LED devices from the detected electric signals and compare the component signals to the output power level corresponding to the set of test signal data and/or to the respective optical energy levels radiated from the respective LED devices, thereby obtaining the spectral response of the solar cell to the different wavelengths of light.   
     
     
         2 . The process for measuring a spectral response of a solar cell according to  claim 1 , wherein the step c) of separating the component signals contributed by the respective LED devices and comparing the component signals to the output power level further comprises the sub-steps of:
 c1) multiplying the respective test signals of the test signal data with the detected electric signals, so that portions of the detected electric signals which are orthogonal to the test signals multiplied therewith and noise portions of the detected electric signals which are independent from the test signals are calibrated to be zero;   c2) comparing the respective component signals corresponding to the respective test signals to the corresponding output power level and/or to the respective optical energy levels radiated from the corresponding LED devices to obtain the energy conversion efficiency corresponding to the respective test signals, and defining the spectral response of the solar cell with respect to the respective central wavelengths of light emitted from the respective LED devices powered according to the respective test signals; and   c3) performing calculation with respect to the respective central wavelengths of light to obtain the overall spectral response of the solar cell.   
     
     
         3 . The process for measuring a spectral response of a solar cell according to  claim 1 , wherein the mutually orthogonal test signals in the step a) are generated based on the CDMA technology. 
     
     
         4 . The process for measuring a spectral response of a solar cell according to  claim 1 , further comprising, before the step a), a step d) of measuring respective luminous intensities of the respective LED devices as powered by the output power level. 
     
     
         5 . An apparatus for measuring a spectral response of a solar cell, comprising:
 a light-emitting diode (LED) array comprising at least one group of LED devices with each group having a plurality of LED devices, wherein the LED devices are capable of emitting multiple types of light having different central wavelengths from one another and the different types of light have a total number equal to or less than the total number of the LED devices;   a driver device for powering the at least one group of LED devices to emit light in a synchronized manner by providing a set of test signal data composed of multiple test signals, wherein the test signals are mutually orthogonal to one another and have an output power level corresponding to at least one known power level; and   a processor device for converting detected values generated by the solar cell upon detecting light from the group of LED devices powered by the set of test signal data into detected electric signals, and for separating component signals contributed by the respective LED devices from the detected electric signals and comparing the component signals to the output power level corresponding to the set of test signal data and/or to the respective optical energy levels radiated from the respective LED devices, thereby obtaining the spectral response of the solar cell to the different wavelengths of light.   
     
     
         6 . The apparatus for measuring a spectral response of a solar cell according to  claim 5 , wherein the driver device comprises a plurality of driver circuits for outputting the test signals to power the respective LED devices to emit light, wherein the test signals are mutually orthogonal to one another and have an output power level corresponding to at least one known power level. 
     
     
         7 . The apparatus for measuring a spectral response of a solar cell according to  claim 5 , wherein the driver device further comprises a CDMA encoder for encoding the mutually orthogonal test signals. 
     
     
         8 . The apparatus for measuring a spectral response of a solar cell according to  claim 5 , wherein the LED light source array includes at least three LED devices capable of emitting light with central wavelengths of red, green and blue light, respectively. 
     
     
         9 . The apparatus for measuring a spectral response of a solar cell according to  claim 5 , wherein the processor device comprises a digital signal processor for separating the component signals contributed by the respective LED devices by multiplying the respective test signals of the test signal data with the detected electric signals, and for comparing the respective component signals to the corresponding output power level and/or to the respective optical energy levels radiated from the corresponding LED devices to obtain the energy conversion efficiency corresponding to the respective test signals, and defining the spectral response of the solar cell with respect to the respective central wavelengths of light emitted from the respective LED devices powered according to the respective test signals, and for obtaining the overall spectral response of the solar cell by performing calculation with respect to the respective central wavelengths of light. 
     
     
         10 . A process for compensating for decay of a light source mounted on an apparatus used for measuring the quantity of electrical energy converted by a solar cell under test, wherein the light source is a light-emitting diode (LED) array for emitting light towards the solar cell, the LED array comprising at least one group of LED devices with each group having a plurality of LED devices, wherein the LED devices are capable of emitting multiple types of light having different central wavelengths from one another and the different types of light have a total number equal to or less than the total number of the LED devices, and wherein the apparatus is stored with reference spectral response values of at least one reference solar cell having a known spectral response to the different wavelengths of light emitted from a standard light source, the process comprising the steps of:
 e) placing the at least one reference solar cell having known spectral response at a test position where the solar cell under test is to be placed;   f) powering the at least one group of LED devices to emit light in a synchronized manner by providing a set of test signal data composed of multiple test signals, wherein the test signals are mutually orthogonal to one another and have an output power level corresponding to at least one known power level;   g) converting detected values generated by the reference solar cell upon detecting light from the group of LED devices powered by the set of test signal data into detected electric signals; and   h) using a processor device to separate component signals contributed by the respective LED devices from the detected electric signals and compare the component signals to the reference spectral response values with respect to the different wavelengths of light, thereby obtaining the deviations of luminous intensity between the light source and the standard light source over the different wavelengths of light.   
     
     
         11 . The process for compensating for decay of a light source according to  claim 10 , wherein the step h) of separating the component signals contributed by the respective LED devices and comparing the component signals to the reference spectral response values further comprises the sub-steps of:
 h1) multiplying the respective test signals of the test signal data with the detected electric signals, so that portions of the detected electric signals which are orthogonal to the test signals multiplied therewith and noise portions of the detected electric signals which are independent from the test signals are calibrated to be zero;   h2) comparing the respective component signals corresponding to the respective test signals to the reference spectral response values corresponding to the standard light source, and defining the deviations of luminous intensity of the light source with respect to the respective central wavelengths of light emitted from the respective LED devices powered according to the respective test signals; and   h3) performing calculation with respect to the respective central wavelengths of light to obtain the deviations of luminous intensity of the light source over all of the different central wavelengths.   
     
     
         12 . The process for compensating for decay of a light source according to  claim 10 , wherein the apparatus further comprises a driver device for powering the light source to emit light by providing the set of test signal data, and wherein the process further comprises, after the step h), a step i) of adjusting the set of test signal data to compensate for the deviations of luminous intensity between the light source and the standard light source with respect to the respective wavelengths of light. 
     
     
         13 . The process for compensating for decay of a light source according to  claim 10 , wherein the apparatus further comprises a driver device for powering the light source to emit light by providing the set of test signal data, and the driver device has a predetermined upper limit for power output, and wherein the process further comprises the steps of:
 j) after the step h) of obtaining the deviations of luminous intensity between the light source and the standard light source with respect to the respective wavelengths of light, determining whether, if the set of test signal data are adjusted into an adjusted set of test signal data to compensate for the deviations of luminous intensity, any of the test signals in the adjusted set of test signal data will result in an output power exceeding the predetermined upper limit for output power;   k) if there is no any test signal in the adjusted set of test signal data that will result in an output power exceeding the predetermined upper limit for output power, allowing the set of test signal data to be adjusted into the adjusted set of test signal data to compensate for the deviations of luminous intensity between the light source and the standard light source with respect to the respective wavelengths of light;   l) if there exists at least one test signal in the adjusted set of test signal data that will result in an output power exceeding the predetermined upper limit for output power, adjusting the at least one test signal to that which will lead to an output power equal to the predetermined upper limit for output power; and   m) recording the adjusted signal of the at least one test signal which will lead to an output power equal to the upper limit for output power, so as to allow the processor device to perform compensation based on the recorded adjusted signal during a later operation of the apparatus.